The need to identify people is ancient. Perhaps the oldest known identification method is the one based on a fingerprint of a person. Already thousands of years B.C.E. various documents were authenticated by making an impression of a finger on a seal. In the early 1900's, crime investigators begun utilizing fingerprints in their work because by that time it had been ascertained that fingerprints were unique to each person and that they do not change during the lifetime of a person. Special fingerprint matching equipment were developed in the 20th century to optically compare fingerprints and look for matches in existing databases.
Reliable automatic identification of individuals is a growing problem. More and more often people manage their bank and other affairs using apparatus that require reliable user identification. This is usually accomplished through the use of an identification number or the like. Such identification numbers or code words may be called personal identification codes or PIN codes. With a four-digit PIN code there is one chance out of a ten thousand that an unauthorized user will accidentally find the PIN code of another person. Since there are numerous different service systems used by people, there are also a great number of different security codes needed. Remembering all those codes may be difficult, especially for older people. If, on the other hand, a person uses one and the same code in many systems, there is the risk that if a code is found out in one system, the code of the person can be illegally applied also in all other systems used by the person.
These problems have led to the development of various automatic biometric identification methods. In such methods the identification of an individual is based e.g. on the identification of a fingerprint, shape of the hand, iris or eyeground of an eye, shape of the face, voice or, in conjunction with a keyboard, the key-pressing dynamics of the user. In any automatic identification, the identification of a person is based on the use of a template where characteristics of the person in question are saved in condensed form. On the basis of a matching process, the person is either identified or not. The identification task may be “one-to-many”, as in a crime case, or “one-to-one”, which e.g. replaces the use of a PIN code in connection with various service automata. The latter method is usually called verification.